Abstract
Changes of dynamic modulus and loss tangent of the composite sheet of low density polyethylene steel under repeated plane bending were measured by means of forced exciting bending vibration resonance method at low frequency.There are three stages of the dynamic modulus changes; the first the modulus decreases with increasingnumber of repeating cycles, the second it is almost constant, and in the last stage the modulus changes markedlyand shows rapid decreases at the instant close to the fracture.
The changes of loss tangent had a contrary tendency to the modulus changes. The starting point of each state, the period of duration and the degree of changes are closely related to the amplitude in the fatigue test. Thisresult is similar to that obtained for FRP or FRTP. The fracture surfaces in T-type peel test were observed by E.M.X for unfatigued and fatigued specimens with the conclusion that the modulus changes occurred in thevicinity of the boundary layer
